Heat developable light-sensitive materials often contain bases or base precursors for the purpose of accelerating heat development. Base precursors capable of releasing basic materials upon thermolysis are preferred because of the shelf life of the light-sensitive materials containing the same.
Typical base precursors are described in U.K. Pat. No. 998,949. The preferred base precursors are salts of carboxylic acids with organic bases. The preferred carboxylic acids include trichloroacetic acid, trifluoroacetic acid, etc., and the preferred organic bases include guanidine, piperidine, morpholine, p-toluidine, 2-picoline, etc. A particularly useful base precursor is guanidine trichloroacetate as described in U.S. Pat. No. 3,220,846. Also, preferred are aldonamides as described in Japanese Patent Application Kokai No. 50-22625, which decompose at elevated temperatures to form a base.
However, many prior art base precursors require a relatively long period of time to produce images with accompanying severe fog. As these base precursors are labile in air and humidity, they tend to decompose under normal conditions, undesirably changing the photographic characteristics of the associated light-sensitive materials and substantially reducing the shelf life thereof.